Patent document 1 describes an example of an internal combustion engine including a ratchet-type one-way clutch arranged between an output shaft of a cranking motor and a crankshaft to transmit torque from the output shaft of the cranking motor to the crankshaft and block the transmission of torque from the crankshaft to the output shaft of the cranking motor. In such a ratchet-type one-way clutch, a pocket is arranged in an inner circumferential surface of an outer ring, which is coupled to the crankshaft. Further, a hook is tiltably supported in a radial direction at a corner of the pocket. An inner ring, which is coupled to the output shaft of the cranking motor, includes an engagement portion that engages the hook. A spring constantly biases the hook toward the radially inner side, that is, in a direction of engagement with the engagement portion.
In such a ratchet-type one-way clutch, when the rotation speed of the outer ring reaches a predetermined rotation speed, which is higher than a cranking rotation speed of the cranking motor and lower than an idle rotation speed of the internal combustion engine, the centrifugal force acting on the hook tilts the hook toward the radially outer side against the biasing force of the spring. This disengages the hook from the engagement portion. Thus, the torque transmission from the ring gear to the crankshaft is blocked. Further, the torque transmission from the crankshaft to the ring gear is blocked by a ratchet mechanism formed by the engagement portion and the hook.